This invention relates to new solvents for chitin and their use in the purification of chitin.
Chitin is an aminocellulose derivative that occurs widely in nature, for example, in the cell walls of fungi, bovine cartilage, cuttlefish bone and the hard shell of insects and crustaceans. The waste from shrimp, lobster and crab seafood industries contains 10-15% chitin and is a potentially important source of chitin, although the isolation and purification of the chitin, associated therein with mineral components, protein and other ingredients, presents considerable difficulty.
The applications for chitin are not extensive, in part because it has been little investigated and in part because it is difficult to purify. The use of chitin for accelerating and promoting wound healing is described in U.S. Pat. No. 3,632,754, to L. L. Balassa, Jan. 4, 1972. In other literature, the difficulties of purification are mentioned frequently. Chitin is also employed in the manufacture of chitosan, a deacetylated chitin that is readily soluble in dilute acids and may find application in paper making and surface active agents, for example.
More specifically, chitin is a mucopolysaccharide, believed to be poly-N-acetyl-D-glucosamine, with an empirical formula of (C.sub.8 H.sub.13 O.sub.5 N).sub.n in which n may be any number into the thousands range, but is commonly in the area of 100-10,000. Chitin is a generally intractable material, soluble only in strong mineral acids, lithium thiocyanate solutions, and other special concentrated salt solutions, most of which cause disintegration or rapid degradation with loss in molecular weight or hydrolysis of the acetyl groups or both.
More recently some new solvents for chitin are described by Paul R. Austin in U.S. Pat. No. 3,879,377, Apr. 22, 1975, and in U.S. Pat. No. 3,892,731, July 1, 1975. These solvents comprise a 1,2-chloroalcohol in admixture with an acidic solvent, e.g. sulfuric acid, and a chloracetic acid alone or in combination with other solvents, e.g. formic acid. These solvents provide useful means for purifying chitin and for regenerating the chitin in the form of films, fibers and the like. However these solutions of chitin are not as stable as desired for storage for considerable lengths of time.
In the isolation and utilization of chitin it is desirable to set specifications for the chitin material, for example, molecular weight, viscosity or optical activity. All of these properties require a stable non-degrading solvent for their determination; the solvents of the prior art give transient values that are difficult to duplicate because of continuing chitin degradation.
It is an object of this invention to provide a new class of solvents for chitin.
It is a further object to provide a method for preparing solutions of chitin that can be filtered, otherwise purified, processed, or their properties measured.
It is still another object to provide solutions of chitin from which the chitin can be regenerated in the form of films, fibers or other shaped objects.
It is a still further object to provide chitin solutions that are stable on storage for considerable periods of time.